The term compensation chuck is used to denote a clamping chuck which by virtue of an unequal movement of its clamping jaws is capable of clamping even workpieces which are not perfectly cylindrical or symmetrical but deviate from a strictly symmetrical shape. The state of the art discloses for example three jaw chucks or six jaw chucks which can provide for limited compensation between the clamping jaws by way of pendulum bridges and similar mechanisms. Basically it is to be noted that any workpiece is elastically deformed by being clamped in a clamping chuck. The elastic deformation means that a workpiece which is machined in a clamped condition, after being removed from the chuck, no longer exactly corresponds in its shape, by virtue of the elastic return deformation, to the state in which it was during the clamped condition.
That deformation is correspondingly more pronounced, the fewer clamping jaws are used for clamping the workpiece. For that reason four-jaw chucks which the present invention involves are viewed as being advantageous over three jaw chucks because they permit more uniform clamping of the workpiece. Centric clamping of workpieces is a central aspect in the case of four-jaw chucks, by virtue of the static over-determination with four jaws, and that aspect is to be taken into consideration in design. To ensure a sufficiently high level of reproduction accuracy and reliability in terms of clamping it is a matter of substantial significance that the chuck always clamps the workpieces in relation to the same center point—and thus centrically. There are various approaches for affording centricity. For example a compensation chuck is known from the publication DE 10 2013 201 231 B3, which ensures centric clamping by means of a guidingly supported drive slider.
The publication WO 2011/137884 A1 discloses for example a compensation chuck. The compensation chuck of the foregoing kind as referred to in the opening of this specification endeavors to ensure centricity of the clamping operation by means of a coupling swing drive. That approach is disadvantageously viewed as being susceptible to trouble by virtue of its complexity. In addition unfavorable lever ratios involve adverse effects on the efficiency in terms of force transmission.
Therefore the object of the invention was to improve a compensation chuck of the kind set forth in the opening part of this specification in such a way that centricity in clamping is improved while chuck assembly complication alleviated as far as possible.